Planting zones have very little to do with gardening; they were designed to measure average winter temperatures throughout North America and which plants survive when planted in those zones. The official name for these zones is the USDA Plant Hardiness Zones.
The USDA has divided North America into eleven zones, zone one being the coldest, where the average temperature can hit –50 degrees Fahrenheit in the heart of the cold season. And zone eleven is the warmest, where it never gets colder than 40 degrees Fahrenheit. The average temperatures can help you know just how much cold a plant can withstand. If a plant is hardy in zone six, it can stand cold down to –10F. That doesn’t mean that you should plant this plant during the cold season; instead it means that if it were planted in the normal planting season, it would live through the winter months.
Along with your zone, you will need to think about the average date for the first and last frost – and if you live in a microclimate that adds other variables to your region – to know when it is safe to plant. Although your USDA zone can be helpful in narrowing down the plants that will thrive in your area, you may want to take your research a step further.
Gardening – By The Book
When looking for plants that will thrive in my area, I have found an invaluable resource in Sunset Magazine’s Western Garden Book. Not only does it break down the country into 24 climate zones (13 more than the USDA), it also has a comprehensive plant encyclopedia where by you can look up the plants that you are interested in planting and see if it will tolerate your specific climate. This gardening guide can also give you landscape ideas with color pictures and tell you how to handle the pests that can attack all of the plants in your gardens. If you have never planted anything before, the Western Garden Book can walk you through your garden from the planning process to harvest day.
For example, I live in northwestern Nevada, close to the California border. According to this book, I live in Zone 3 – the mildest of the high elevation and interior climates. The average lowest temperatures in this region ranged from 13 degrees Fahrenheit to –24 degrees Fahrenheit over a twenty-year period. The average growing season is about 160 days long.
If I am looking to add a specific plant to my vegetable garden – say, cauliflower—I would turn to the section on plant care under the subheading ‘Vegetables’ and look up cauliflower in the chart to see if it would grow in my climate zone. It does. They recommend planting it from seedling plants you would purchase from your local garden supply or home center. Planting time, by the book, is May-June, and it says cauliflower takes 60 to 100 days to reach its harvest date. Don’t be afraid to combine this knowledge with your own observations though. For example, I don’t usually plant anything outside before the 1st of June, as snow can fall very late in spring and sometimes even in early summer in my area.
If I needed to see planting specifics and what pests were common to the cauliflower, I would find the entry for cauliflower in the plant encyclopedia. It spells out planting distances, time lines for staggering the crop, when to fertilize and what type of fertilizer to use, as well as how to control aphids and other common pests.
Other Gardening Issues
Zone requirements are also important when considering what kind of landscaping you want to incorporate on your property or whether you can add certain types of fruit or nut trees to your orchard. I have used my Sunset Western Garden Book to give me the necessary information for all of these reasons and more. Edible figs grow well in zones 4-9 and 12-24. Most eucalyptus trees can survive in zones 8-24. Persimmons and blackberries will grow in various zones. And Bearded irises and narcissus can grow in any zone.
Find yourself a good reference for planting in your region and follow its suggestions for growing the various plants on your property. Yours may very well be the same as mine – Sunset Western Garden Book. Another reference is the Farmers Almanac – both online and in magazine format. Grow, eat, and enjoy gardening by your climate zone!